An index cover houses the index of a meter, such as a gas flow meter, and protects the index from the elements to which the flow meter may be subjected. In many installations, the meters are outdoors and subjected to rain, sun, and dirt, or though indoors or partially protected from the elements, still located in dirty and moist environments. While the juncture of the index cover to the remainder of the meter is generally sealed, the effectiveness of the seal has not been considered crucial to the function of the meter. Thus, prior art index covers have incorporated seals of marginal integrity that, for the most part, seal water and other contaminates out of the interior of the index cover, but that still allow a small amount of leakage. Others have even included vent passages in the seals or index covers to allow communication of air and moisture between the interior and exterior of the index cover, thus intentionally facilitating leakage. As is apparent from the marginal seals of the prior index covers and inclusion of vent passages in many seals, the value of an effective seal between the index cover and the remainder of the meter has heretofore gone unappreciated.